Pennyroyal

Related Terms

Aloe herbal horse spray, alpha-pinene, American false pennyroyal, American pennyroyal, beta-pinene, brotherwort, chasse-puces, churchwort, Cunila pulegioides, dictamne de Virginie, European pennyroyal, fleabane, flea mint, fretillet, Hedeoma phlebitides, hedeomal, herbal horsespray, herbe aux puces, herbe de Saint-Laurent, Iranian Mentha pulegium, Labiatae (family), la menthe pouliot (French), Lamiacae (family), lurk-in-the-ditch, Melissa pulegioides, mentha pouillot, menthone, Miracle Coat spray-on dog shampoo, mock pennyroyal, mosquito plant, Old World pennyroyal, paraffins, pennyroyal essential oil, petit baume, piliolerial, piperitenone, poley, pouliot royal, pudding herb, pudding grass, pulegium, pulegium oil, Pulegium vulgare, pulegone, pulioll-royall, Pulegium regium, run-by-the-ground, squaw balm, squaw mint, squawmint, stinking balm, tannins, terpenes (pulegone), tickweed.
Combination product example: PNC (contains pennyroyal, red raspberry, lobelia, blue cohosh, black cohosh, and blessed thistle).

Background

The essential oil of pennyroyal is considered toxic. Death has been reported after consumption of the extract and oil. A characteristic noted in most cases of pennyroyal overdose is a strong minty smell on the person's breath. Menthofuran, a toxic compound found in pennyroyal, can be detected in the urine, blood, or other tissues. Overdose management includes washing out the mouth and/or taking activated charcoal as an emergency treatment for poisoning.
Liver failure caused by pennyroyal is similar to liver failure caused by acetaminophen (Tylenol?). Since N-acetylcysteine (NAC) is used to treat liver failure caused by acetaminophen, it may also be used to treat liver failure caused by pennyroyal. More research is needed in this area.
Historically, the essential oil of pennyroyal has been used as an abortion inducer and menstrual flow stimulant. Yet, it may do so at lethal or near-lethal doses, making this action unpredictable and dangerous. Additional studies focusing on the less toxic parts of the pennyroyal plant and the menstrual cycle are needed before a conclusion can be reached.

Evidence Table

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *


Traditionally, pennyroyal oil has been used to cause abortion. However, the use of pennyroyal is dangerous and illness and death have been reported.

 C


Traditionally, pennyroyal oil has been used to cause abortion. However, the use of pennyroyal is dangerous and illness and death have been reported.

 C


Traditionally, pennyroyal oil has been used as a menstrual flow stimulant. However, the use of pennyroyal is dangerous and illness and death have been reported. Additional research is needed on the pennyroyal plant and the menstrual cycle.

 C


Traditionally, pennyroyal oil has been used as a menstrual flow stimulant. However, the use of pennyroyal is dangerous and illness and death have been reported. Additional research is needed on the pennyroyal plant and the menstrual cycle.

 C
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)

Tradition / Theory

The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

Dosing

Adults (18 years and older)
Note: There is no proven safe or effective dose for pennyroyal. The following doses have been used, but may be toxic.
In the form of a pennyroyal extract (1:2), weekly doses of 20-40 milliliters have been taken by mouth, but may be toxic.
In the form of an oil, doses of 0.5-3 drops have been taken by mouth, but may be toxic.
In the form of a tea/infusion, 1-2 cups of tea made from 1-2 teaspoons of dried leaves per cup of boiling water, steeped for 10-15 minutes have been taken by mouth daily, but may be toxic. For cough, congestion, and upset stomach, a tincture of 1.25-2.5 milliliters of pennyroyal in tea water has been taken by mouth up to twice daily, but may be toxic.
In the form of a tincture, doses of 30-60 drops have been taken by mouth twice daily or 1-2 milliliters have been taken by mouth three times daily, but may be toxic.
If an essential oil is to be used on the skin, it should first be mixed with another oil. The dilution ratio may vary. A 2 percent dilution is sometimes used when making whole body oil or lotions, and a 1 percent dilution is sometimes used for children and the elderly. However, safety and effectiveness are unproven, and skin preparations have been associated with side effects throughout the body.
For use as an insect repellent, crushed plant material and a pennyroyal tincture mixed with skin cream have been rubbed on the body, but may be toxic.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Interactions

Interactions with Drugs
Pennyroyal may interfere with the way the body processes certain drugs using the liver's "cytochrome P450" enzyme system. As a result, the levels of these drugs may be increased in the blood, and may cause increased effects or potentially serious adverse reactions. People using any medications should check the package insert and speak with a healthcare provider or pharmacist about possible interactions.
Pennyroyal may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. People taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare provider, including a pharmacist. Medication adjustments may be necessary.
Many tinctures contain high levels of alcohol, and may cause nausea or vomiting when taken with metronidazole (Flagyl?) or disulfiram (Antabuse?).
Pennyroyal may also interact with acetaminophen (Tylenol?), agents that are toxic to the liver, agents that increase seizure risk, agents that induce abortion, antiandrogens, antibiotics, anticancer agents, anti-estrogens, antihistamines, fertility agents, hormonal agents, and insect repellents.

Attribution

This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography

Anderson IB, Mullen WH, Meeker JE, et al. Pennyroyal toxicity: measurement of toxic metabolite levels in two cases and review of the literature. Ann Intern Med 4-15-1996;124(8):726-734.
Anderson IB, Nelson SD, and Blanc PD. Pennyroyal metabolites in human poisoning. Ann Intern Med 1997;126(3):250-251.
Bakerink JA, Gospe SM Jr, Dimand RJ, et al. Multiple organ failure after ingestion of pennyroyal oil from herbal tea in two infants. Pediatrics 1996;98(5):944-947.
Black DR. Pregnancy unaffected by pennyroyal usage. J Am Osteopath.Assoc 1985;85(5):282.
Buechel DW, Haverlah VC, and Gardner ME. Pennyroyal oil ingestion: report of a case. J Am Osteopath Assoc 1983;82(10):793-794.
Carmichael PG. Pennyroyal metabolites in human poisoning. Ann Intern Med 2-1-1997;126(3):250-251.
Ciganda C, and Laborde A. Herbal infusions used for induced abortion. J Toxicol.Clin.Toxicol 2003;41(3):235-239.
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Giorgi DF, Lobel D, Morasco R, et al. N-acetylcysteine for pennyroyal oil toxicity. Vet Human Toxicol 1994;36(4):358.
Khojasteh-Bakht SC, Chen W, Koenigs LL, et al. Metabolism of (R)-(+)-pulegone and (R)-(+)-menthofuran by human liver cytochrome P-450s: evidence for formation of a furan epoxide. Drug Metab Dispos 1999;27(5):574-580.
Mack RB. "Boldly they rode ... into the mouth of hell". Pennyroyal oil toxicity. N.C.Med J 1997;58(6):456-457.
Martins HM, Martins ML, Dias MI, et al. Evaluation of microbiological quality of medicinal plants used in natural infusions. Int J Food Microbiol 8-15-2001;68(1-2):149-153.
Mazur LJ, De Ybarrondo L, Miller J, et al. Use of alternative and complementary therapies for pediatric asthma. Tex.Med 2001;97(6):64-68.
Perez-Calderon R, Gonzalo-Garijo A, Bartolome-Zavala B, et al. Occupational contact urticaria due to pennyroyal (Mentha pulegium). Contact Dermatitis 2007;57(4):285-286.
Sullivan JB Jr, Rumack BH, Thomas H Jr, et al. Pennyroyal oil poisoning and hepatotoxicity. JAMA 12-28-1979;242(26):2873-2874.